It isn’t difficult so long as you can find somewhere with clean air and plenty of suitable rock. This one was taken on the Long Mynd, Shropshire. Other good places are the English Lakes. We have too much pollution from Bath to get really good ones here, though. It isn’t a very good picture but the rock is covered in different lichens; at least 5 different species are visible. Grass on left to give an idea of scale.
Nothing so innocuous. Once a month he turns into an evil fungus/algae symbiont that can chew its way through rock that would cause a werewolf to break its teeth.